1. Field of the Invention
The present invention relates to a light source device for an endoscope.
2. Description of the Related Art
Endoscopes are widely used in medical and other fields. An endoscope comprises a long thin insertion unit. Endoscopes allow observations to be made of organs and body tissues in body cavities and also allow various treatments employing instruments inserted into an instrument insertion channel as necessary.
In an endoscope apparatus comprising such an endoscope, the subject body illuminates the object site by guiding illuminating light from a light source device employing a light guide etc., and an endoscope image is obtained by capturing the reflected light.
The above endoscope apparatus can capture an image by an endoscope image capturing means, and perform signal processing by a signal processor device (hereinafter referred to as “processor”), and display endoscope image on an observation monitor. Consequently body tissues can be observed.
As described above, an endoscope system comprises a light source device for supplying illuminating light to a light guide incorporated in the endoscope in order to irradiate the subject body. The light guide is used in combination with a light source device, and there are a variety of types of light guides. For example, in a type of light guide with a small incident end diameter, if the input illuminating light is too bright, it is probable that the heating value of the irradiated part in body cavities will become excessively large. Hence, when the endoscope is in use, the brightness of the supplied illuminated light has to be adjusted in accordance with the type of light guide. Consequently a light source device for an endoscope is disclosed that it should be able to obtain the appropriate brightness and light distribution of the illuminating light in accordance with the type of light guide connected to the light source device of an endoscope (for example, Patent Document 1).
FIG. 1 is a construction diagram of such a light source device for an endoscope. The light source device of FIG. 1 comprises light guide connector identifying means 81 and 82, limiting means 80, and light intensity adjustment means. The light guide connector identifying means 81 and 82 identifies the type of light guide connector 83 to be connected. The limiting means 80 limits the illuminating light that will be on the optical path of the illuminating light. The light intensity adjustment means appropriately adjusts the light intensity of the illuminating light incident on the light guide in accordance with the type of light guide connector 83 identified by the identifying means 81 and 82. In order to prevent the tip of the light guide from causing burns and heat damage in body cavities, it is possible to supply illuminating light with appropriate brightness to the endoscope so that the brightness of the incident illuminating light is not excessively intense, even if the endoscope has a light guide with a small incident end diameter.
In an endoscope apparatus, in usual cases of body tissue observation, the light source device emits white light (hereinafter referred to as normal light) in the visible light range, illuminates the object site of the subject body as frame sequential light by passing through a rotating filter such as RGB, for example, performs image processing by synchronization of an image signal based on the reflected light by a processor, and finally obtains color images (hereinafter referred to as the frame sequential method).
Alternatively, the endoscope apparatus is provided with color chips in front of the imaging area of a solid-state image sensor installed in the endoscope, captures images by separating the reflected light of the normal light into RGB in the color chips, performs image processing via a processor, and obtains color images (hereinafter referred to as the simultaneous method).
A variety of endoscope apparatuses for special light observations have been proposed since the optical absorption property and the optical scattering property are different according to the wavelength of the irradiating light in the body tissue.
For example, as a frame sequential method, as described in Japanese Patent Application Publication No. 2002-336196, an endoscope apparatus for fluorescent observation, which makes a diagnosis by utilizing a difference between normal tissue and lesions in autofluorescence generated from the body tissue by irradiating pump light such as ultraviolet rays and blue light on a body tissue, has been proposed in recent years.
As described in Japanese Patent Application Publication No. 2000-41942, an endoscope apparatus for infrared light observation, which enables an observation of the depth of the body tissue by irradiating infrared light on the body tissue as illuminating light, has been also been proposed. In addition, as described in Japanese Patent Application Publication No. 2002-95635, an endoscope apparatus for narrow-band light observation, which enables an observation around a superficial portion of the mucous membrane of the body tissue by irradiating the body tissue with blue narrow-band light as illuminating light, has been proposed.
Endoscopes used for the above observations need to be able to make at least two types of observations, a normal light observation and at least one special light observation. For example, with the use of the endoscope for fluorescent observation, normal light observation and fluorescent observation are possible. With the use of the endoscope apparatus for infrared light observation, normal light observation and infrared light observation are possible. Normal light observation and narrow-band light observation are possible using the endoscope apparatus for narrow-band light observation.
Similarly, in the simultaneous method, at least one special light observation in addition to normal light observation can be conducted, and, for example, normal light observation and a narrowband light observation are possible with the use of a narrowband light observation endoscope, and normal light observation and a fluorescent observation are possible with the use of a fluorescent observation endoscope.
In these endoscopes for special light observation, the switching operation between normal light observation and special light observation is performed by operating an operation unit of the endoscope, a processor, a switch provided on the front panel of the light source device, or a foot switch for the endoscope, etc.
In recent years, there have been increasing demands for a plurality of special light observation modes to be available to be used with one set of processor and light source device. The usage depends on the user, particularly whether the endoscope will be used for internal medicine or for surgery. For example, a physician may use an endoscope as a narrowband observation endoscope, a surgeon may use the endoscope as a fluorescent observation endoscope, and another surgeon may use the endoscope as an infrared light observation endoscope.
Here, the special light observations have different spectroscopic characteristics for the illuminating light supplied from the light source device, different transmission characteristics of the objective optical system of the endoscope, different types of solid-state image sensors, and different signal processing in their processor devices, etc., in accordance with the observation mode.
As described above, conventional light source devices are provided with filters for special light observation modes in an observation mode switching turret comprising a plurality of observation mode filters corresponding to the observation mode.
Patent Document 1:
Japanese Patent Application Publication No. 2003-210403
Patent Document 2:
Japanese Patent Application Publication No. 2002-336196
Patent Document 3:
Japanese Patent Application Publication No. 2000-41942
Patent Document 4:
Japanese Patent Application Publication No. 2002-95635